AZD6244 (ARRY-142886) is an investigational anticancer drug that is designed to block a critical component (MEK (methyl ethyl ketone)) of a pathway (MAP (mitogen-activated protein) kinase pathway) that causes some lung cancer cells to grow. The MAP kinase pathway could be overactive in a proportion of lung cancers, including some which also have another mutation in a protein known as KRAS (Kirsten rat sarcoma viral oncogene homolog). Approximately 20% of lung cancers have KRAS mutations which can make some cancer treatments including erlotinib, a standard anticancer treatment drug less effective. Researchers are interested in determining whether AZD6244 is effective in treating advanced NSCLC (non small cell lung cancer), including KRAS mutated lung cancer that has not responded to standard therapy.